The present invention relates to a drawing and coloring element in the form of a drawing stick for producing pictures that can be fixed through the application of heat.
There are already known drawing and/or painting, i.e. coloring elements in the form of sticks having a certain thickness and consisting of extruded chalk and/or gypsum and possibly color-producing pigments. The pictures, inscriptions or drawings made with such chalks cannot be fixed on the base through simple means and in lasting manner. The same is true for the great number of colored pencils available on the market.
Further, it is already known to produce colored patterns on bases, such as ceramic plates, metal plates, etc., through the application of a paste consisting of fusible mineral powders and subsequent heating of the mineral powders to the fused state. Such production takes place in two steps: a surface layer, the so-called base mineral, is first established in the base and only to such surface layer one applies the colored pattern, which is stoved or burned in, with a further firing operation.
These processes require the use of firing temperatures in the range of about 800.degree. C., the use of special, expensive enamel dyes, that frequently do not correspond in their color tone to the color obtained after the firing, or the use of colored top-enamel powders. The preparation of colored patterns in accordance with the enameling process is thus bound to the use of a special and costly kiln for producing the necessary firing temperatures and requires a substantial knowledge of the art, so that one must exclude in advance a general use of such methods, e.g. for the hobby-type production of lasting color patterns or pictures on resistant bases, such as sheet metal, glass, etc.
Further, there are known colored pencils consisting of pigments and synthetic resins. However, owing to the fact that the "lead" consists of a hard fusible element similar to the "leads" used in "lead pencils," such colored pencils cannot be used as drawings or coloring elements in the form of blackboard type chalks for producing in blackboard-chalk fashion pictures that can additionally be fixed on bases through the application of heat.
For example, the Mukai et al U.S. Pat. No. 3,834,910 describes a "pencil lead" based on a powdered coloring agent, a thermoplastic epoxy resin, metal soaps and customary additives, the "lead" being characterized in that it exhibits good strength and hardness, and is formed by melt extrusion of the thermoplastic composition. The mixture consisting of thermoplastic and additives is extruded into "leads" at temperatures of at least 140.degree. C., the "leads" being then processed into pencils of customary degrees of hardness.
Similarly, the Ishida et al, U.S. Pat. No. 4,017,451 discloses the manufacture of a colored pencil lead of great bending strength from a molten mass of thermoplastic novolak resin and coloring agent, as well as optional ingredients such as other thermoplastics, lubricants, etc.